Pull-out strength evaluation of cement augmented iliac screws in osteoporotic spino-pelvic fixation.

ABSTRACT

INTRODUCTION: Spino-pelvic fixation has been widely accepted for surgical treatment of sacral tumor, scoliosis surgery and pelvic fractures. Cement augmentation of screws is an option to improve implant stability in osteoporotic bone quality. Aim of the present study is to compare iliac screw fixation without cement fixation and two cement application options in a biomechanical testing. HYPOTHESIS: Cement augmentation of iliac screws leads to superior pull-out strength. MATERIAL AND METHODS: Thirty female and osteoporotic human iliac bones were used. Three operation treatment groups were generated Screw fixation (cannulated screws) without cement augmentation [Operation treatment (OT) A], screw fixation with cement augmentation before screw placement (cannulated screws) (OT B) and screw fixation with perforated screws and cement augmentation after screw placement (OTC). Pull-out tests were performed with a rate of 6mm/min. A load versus displacement curve was generated. Maximum pull-out force (N) was measured in the load-displacement curve. RESULTS: Paired group 1 (OT A vs. OT B) Screw fixation without cement augmentation 592.6N±335.07 and screw fixation with cement augmentation before screw placement 996N±287.43 (p=0.0042). Paired group 2 (OT A vs. OT C) screw fixation without cement augmentation 716.2N±385.86 and fenestrated screw fixation with cement augmentation after screw placement 1324.88N±398.76 (p=0.0489). Paired group 3 (OT B vs. OT C) Screw fixation with cement augmentation before screw placement 1077.2±486.66 and fenestrated screw fixation with cement augmentation after screw placement 1298.2N±726.19 (p=0.3286). DISCUSSION: Regarding iliac screw fixation for spino-pelvic ostesynthesis in osteoporotic bone, cement augmentation is significantly superior to solid iliac screw fixation respecting pull-out-strength. Nevertheless, further biomechanical studies are needed to verify these findings. LEVEL OF EVIDENCE Not applicable; biomechanical cadaver study.